Regulation of interleukin-8 by miR-17 during chronic inflammation in cystic fibrosis

Abstract

A symptom of cystic fibrosis (CF) is chronic lung inflammation. MicroRNA (miRNA) profiles between CF bronchial epithelial cells (BECs) differ from that of non-CF BECs. 1 Several studies, including this one, reveal functional roles of miRNAs in CF and lung immunology. Aims: To establish a causal relationship of miR-17 downregulation and CF. To identify miR-17 targets relevant to CF pathophysiology. Methods: In vivo miRNA expression was analysed in human and mouse CF and non-CF lung tissue. miRNA and gene expression was analysed with qPCR and ELISA. Potential miR-17 targets were identified in silico . Further expression studies and miRNA target validation with miRNA mimics/inhibitors and luciferase reporter assays were conducted in inflammatory models of CF and non-CF BECs. Results: MiR-17 was downregulated in human CF airway epithelial tissue compared to non-CF samples. This was confirmed in tracheal tissue of a CF-like β-ENaC-transgenic mouse model, but not in CFTR knockout mouse samples. BEC cultures exposed to 5-day inflammatory stimulation resulted in a downregulation of miR-17, but no base-line difference was found between CFTR- and CFTR+ cell lines. Target analysis revealed miR-17 to target interleukin-8 (IL-8). IL-8 was subsequently validated as a miR-17 target in BEC cultures. Conclusion: We show that miR-17, an important miRNA in the immune system and in lung development, is downregulated in airway epithelial tissue and BECs subjected to chronic CF disease conditions. miR-17 could have a major role in controlling inflammation through regulation of IL-8. 1. Oglesby et al. miR-126 is downregulated in cystic fibrosis airway epithelial cells and regulates TOM1 expression J Immunol 184, 1702–1709 (2010).